1. Field of the Invention
The present invention relates to a current generating system, and more particularly to an alternating current generator used in a motor vehicle for supplying electric power to a battery, electric loads such as lamps and so on.
2. Description of Prior Art
It is recently required for a generating system used in a motor vehicle to produce sufficient electric energy during whole operating conditions, namely at a low speed operation as well as a high speed operation of the generator.
In a general current generator, there is a contrary relationship between output energy at the low speed operation and that at the high speed operation. In other words, the output energy (current) can be increased during the low speed operation when winding turns of generating coils are increased, however the output energy (current) is decreased during the high speed operation by the generator, and vice versa.
To overcome the above drawback, it is conventionally proposed that electrical connections in poly-phase current generating windings of the generator are changed in response to the operating conditions thereof, for example, in a generator of three-phase current generating type, the windings are arranged as three-phase Y-connected windings at the low speed operation and the windings are arranged as respective independent generating windings at the high speed operation.
However, the above proposed generator has the following disadvantages in view of the fact that a plurality of switching elements corresponding to the number of winding phase are required in the proposed generator.
1. An interlocking switching device is required. PA1 2. An unfavorable operation may take place when the plurality of switching elements are not simultaneously closed or opened owing to the transient phenomena. And PA1 3. The output characteristic or life-time of the generator may be badly affected or extremely reduced, when even one of the plurality of the switching elements becomes disordered, since the unbalanced current occurs in the poly-phase generating windings.